I realised that it only kicks in on the primary card once the OS knows your monitor is sleeping / off. If I turn off the monitor, it makes no difference, it actually has to be put into sleep mode by Windows.

I made a shortcut to a G-key on my keyboard using nircmd (nircmd.exe cmdwait 500 monitor off) to switch off the monitor, and it now forces the primary GPU into low power mode (fan stops spinning)

I'm still having issues with the second card; but a kind-of fix in the meantime is if I go into CCC, disable Crossfire, then enable it again right away, the second card will power down as intended a few seconds later. I have to repeat this step wvery restart / wake

None of this is particularly elegant, but it works. (I am using a DVI cable.) Edited by omega17 - 2/24/12 at 7:42am

Interestiong stuff! Thanks for the help, but i'm not switching the monitor off, I'm letting windows put it to sleep, I have it set to switch off after 1 minute at the moment although I normally have it set to 5 minutes... I will try what you are doing though....

Thats a complete pain with crossfire though, having to do that every time you boot, that said I wouldn't mind a second 7970

i had the same problem it was because i had a hdmi cable plugged into the gpu i now have a dvi to hdmi cable plugged in and it works now (even with just one gpu) so try a dvi cable and this should solve your problem. if you want HD get a hdmi to dvi lead but make sure you plug the dvi end to your gpu and the hdmi end to your monitor. also make sure your mouse is set to not wake the computer.

Finally tried a DVI, I didn't have one to hand before now, of course, fan stops moments after the monitor shuts off!!!

I really want to know if this is a permanat thing, does zerocore only work for the DVI connction, or will drivers enable it over displaport... It annoying as displayport handles audio and the cable is so much thinner and neater than the dual link dvi cables... At least I found a dvi with a 90 degree connector which is quite neat.... Be carfull if you are ordering one of the 90 degree DVIs as there are two versions, one which points up and one which points down. I think the one that points up would put alot of stress on the graphics card myself, might be ok if your compter is under your desk but still... My computer is on my desk so the 90 degree downward pointing one should be perfect.....

Thanks everyone for your help, I might emails some of the reviewers to see if they can get an answer from AMD/ATI as to wheter zerocore will ever work over displayport, wish me luck!!

I'm sure it works as long as one of the cables is DVI, I bet you if you use HDMI + Displayport + Displayport doesn't work. It seems the zerocore controller chip is only activated by the monitor connected to the DVI port... Please let me know if you are using one of the monitors on DVI in case I'm wrong, I would be delighted to be!

If it does only work over DVI its a bit of a pain for anyone using it conected to a HD TV.... I really think they should have told people this

I have the same problem with Zerocore also, monitor goes off like it should automatically, and nothing! VGA fans still spinning.... Jeez! even my 5870 used less power at idle!.... 12 watts less than my 7950

I have a strong feeling that the OC applications like Trixx and Afterburner are preventing the GPU from going into Zerocore as it's continuously reading the GPU's status, or taking control of the clocks from CCCEdited by Atomfix - 1/21/13 at 12:16pm